Method of producing substructures for structures



' Oct. 20, 1931. L. WHITE 1,827,921

METHOD OF PRODUCING SUBSTRUCTURES FOR STRUCTURES Filed may 1. 1929 ATTORN EY Patented on. 20, 1931 Tiaras Application filed Kay 1 1929. Serial No. 855L591.

This invention relates to-certain improvements in a method of installing sub-structures for structures, as, for instance, underpinning the foundations of buildings already a erected or in constructing foundations for buildings that are being erected.

In my prior patents, No. 1,217,128, dated Feb. 20, 1917, and No. 1,229,364, dated J nine.

the method of these patents, the footing, such as a pile, was driven until it is brought up, that is, could not be driven further, under a load at least as great as the permanent load it was to carry, and the permanent load was transferred to the pile while under the temporary load. This method of driving and loading the pile produces at its base a compression of the earth which results in the formation of what may be termed a pressure bulb which will not deform under the permanent load the ile isto carry, and as the permanent load is transferred to the pile while under the temporary load, rebounding of the pile is prevented, and no further settlement of the pile occurs.

In carrying out the methodof said patents, as long as the piles or other units of the footing were far enough apart, so that the pressure bulbs under the units did not overlap,

no settlement of the footing occurred. Under some circumstances, however, It was found that settlement occurred, as, for instance, where, owing to the load or the character of the soil, the units of the footing, such as piles, had to be placed so close together that the bulbs of pressure overlapped. This lessened the carrying capacity of a group of adjacent piles; that is, assuming four piles in a group, each designed to carry tons, the four piles would not carry a load of 200 tons if the bulbs of pressure overlapped.

I have discovered that this settlement of the structure can be avoided by driving the individual units of the footin such as a pile, until the pile brings up un er its expected load, and then applying simultaneously to a group of units in the footing a pressure at least as great as the maximum load such group of units is designed to carry, the individual units of the footing being maintained under load during the group setting and while the permanent load is transferred to them. This. application of pressure to the group probably results in the breakin down of the small individual pressure bul s and the formation of a single large pressure bulb under the group of units which will with- I stand the load to be carried by that group of units; but, in any event, this application of pressure to a group of units overcomes the tendency of, the settlements above referred to.

It is the especial object of the invention to provide a method of producing sub-structures for structures in which the supporting units of a footing aretested individually and later in groups, so as to effect the formation of the enlarged pressure bulb which will support the load required from one group of units without settlement.

A further object of the invention is-to so carry out the setting of the groups of units that the entire system of supporting units act as one large unit sustained by an enlarged base of compressed earth or bulb of pressure.

I In order that the method of the present invention may be fully understood, a description of one application of it and a preferred way of carrying it out, will be iven in connection with the aces-meaning rawings in which Fig. 1 re resents the positioning of a single unit of a footing and its pressure bulb.

Fig. 2 represents the positioning of a plurality of units of a footing with the individual pressure bulbs first formed and the enlarged pressure bulb produced by group setting.

Fig. 3 is a diagrammatic plan view of a plurality of units of a footing.

In the following description of carrying out the method, it will be assumed that a. substructure is to be provided for a structure already erected under which the footing supporting the structure must be changed to a lower level because of an excavation adjacent or under the foundation of the structure, but it will be understood that such application of the method is selected as illusrative only, and that the method is not restricted to such application. In thus changing or lowering the supporting foundation of the building or underpinning, as it is technically called, there are excavated comparatively small pits beneath the foundation, the sides of which are or may be supported by wooden sheathing, or in any other suitable manner. In these pits, the individual units of the footing are installed. These individual units may be of various character, but are preferably in the form of piles consisting of sectional steel cylinders which are driven in any suitable manner, as, for example, by means of hydraulic rams. These steel cylinders are cleaned out as they are driven, and after they have been driven to the required depth. they are filled with concrete, each unit thus being in the form of a pile. The hydraulic rams, by which the driving is eflected, bear against a driving plate placed on top of the sectional cylinder being driven, and the rams drive against what is termed a wedging plate positioned between the rams and the foundation of the building. After the pile has been driven to approximately the required depth, pressure is applied to the pile preferably greater than the load the pile is eventually to carry. When the pile stops settling, a supporting post, such as a post of structural steel, like an I-beam, is placed between the driving plate and the wedging plate, adjusting wedges being provided, so that upon release of the temporary pressure or load caused b the rams, practically no rebound of the pile will occur, thus keeping the pressure bulb of earth intact. This operation is preferably repeated until the required number of piles to support the estimated load has been driven. This is diagrammatically illustrated in Fig. 1 of the drawings, in which a pile has been illustrated as driven until the required pressure bulb has been formed, and no further settlement of the individual ile occurs.

As illustrated, the pile is formed of sectional steel cylinders, three sections, 1, 2, 3, belng shown. The driving plate 4 supports two rams 5, 6, which bear' against the Wedging plate 7 which, in turn, seats against a part of the foundation, as 8, of the building or other superstructure. As above explained, after the pile has been driven approximately the required depth, a wedging I-post 9 is interposed between the plates 4 and 7, and cooperating adjusting wedges 10, 11 are interposed between the wedging plate 7 and the top of the post 9. These wedges 10, 11 are of the foundation 8 is transferred to the pile.

The rams may be operated in any suitable manner, as from a pump 12 and suitable piping 13. What may be termed the bulb of pressure formed by this operation is indicated at 14, and, in cases where the piles are far enough apart, so that there is no overlapping of the bulbs of pressure, such pressure bulbs will support the load they are required to carry.

If, however, owing to the necessity of supporting heavy loads, or on account of the character of the soil, the piles have to be placed close together, there probably arises a ground condition in WlllCll the pressure bulbs overlap, so that certain of the bulbs lose part of their supporting area, with the result that a settlement of the piles occurs, the supporting areas of such pressure bulbs being insufiicient to carry the load. Such a condition is illustrated in Fig. 2, where three piles, 15, 16 and 17, are diagrammatically shown, the pressure bulbs beingmarked 18, 19 and 20. Referring to this figure, it will be noted that bulbs overlap, thus reducing the supporting area, and, although each pile unit considered alone might carry its predetermined load, all the piles if left in this condition will not support the aggregate load.

In accordance with the present invention,

this deficiency of the supporting power of a plurality of piles has been found to effectually prevent further settlement under the permanent load, and this is probably due to the formation of a single enlarged pressure bulb extending under the plurality of piles, such as 21 in Fig. 2, this pressure bulb being of sufficient area to support the load required of suchplurality or group of piles. The area. of this enlarged pressure bulb formed under the plurality of piles is greater than the combined area of the individual pressure bulbs.

This application of pressure to a plurality of piles, or, as it may be conveniently called, group setting, may be effected in various ways, as, for instance, all the unit piles making up a footing may be simultaneously set,

pile are driven home, so that there isno rebound of the piles or disintegrating orbreaking down of the enlarged pressure bulb formed by the group setting. The operation is repeated until all the piles of the footing are in their final position, an enlarged pressure bulb being built up under the entire group capable of carrying the load required of all the piles without settlement. 4

The pressure may be applied to the chosen piles simultaneously in any suitable manner, as by hydraulic pump 28, with or Without an accumulator (not shown), pipe 29, and branch pipes 30, 31, 32, each of these branches supplying pressure to the respective driving rams of each pile.

It may be desirable, instead of loading each pile individually, to load a plurality of the piles simultaneously, as by using a plurality of rams, Wedge these piles to transfer the permanent load thereto. and then simultaneously apply to the piles a load as great as the combined load the piles are to carry, the piles being maintained under load during the exchange and during the simultaneous application of the setting load thereto.

By practice of the method described, structures may be underpinned or provided with foundations under such load or ground conditions as would make impossible proper underpinning under prior practice. The method, also, is economical, as a less number of units are required and damage to buildings 7 in underpinning, operations is practically eliminated, thus obviating repair expense.

It will be understood that the method is applicable to the production of foundations for buildings or other structures already erected and While being'erected. The method may also be carried out With supporting units other than cylinders, such as blocks of reinforced concrete. The method is, therefore, not to. be restricted to the application described.-

What is claimed is:

1. The method of providing a substructure for structures, which consists in setting a footing consisting of a plurality of closely adjacent units, loading each unit With a temporary load and maintaining it under such load until settling of the unit ceases, exchanging the temporary load on each unit for the permanent load assigned to it, applying simultaneously to a plurality of units a common temporary load at least as great as the combined common permanent load such plurality of units is to carry whereby an enlarged pressure bulb common to said plurality of units is formed beneath said plurality of units, and repeating the application of the load to another plurality of the units until settling of that plurality ceases, and While each plurality of units is maintained .under its common temporary load. exchanging said load simultaneously as to all the units changing the temporary load on each unit for l a permanent load assigned to it, and thereafter applying simultaneously to a plurality of alternate units a common temporary load at least equal to the combined common permanent load such alternate units are to carry whereby an enlarged pressure bulb common to said plurality of units is formed beneath said plurality of units, the units being maintained under their individually assigned temporary loads during the exchange, then exchanging the common temporary load for their common permanent load While their.

common temporary load is still applied thereto, and thereafter removing their common temporary load.

3. The method of providing a substructure for structures which consists in setting a footing consisting of a plurality of closely adjacent units, loading each unit with an individual temporary load and maintaining it under such load until settling of the unit ceases, exchanging the temporary load for an individual permanent load, applying simultaneously to a plurality of alternate units a. common temporary load at least as great as the combined common permanent load such units are to carry, whereby an enlarged pressure bulb common to said plurality of units is formed beneath said plurality of units. and repeating the application of common temporary load to a different plurality of alternate units until further settling ceases, the units being maintained under load during the exchange from their individual permanent loads to their common temporary loads and while their common temporary load is simultaneously applied thereto.

4, The method of underpinning a structure which consists in driving a plurality of piles closely adjacent each other, loading each pile individually with a temporary load and maintaining it under suchload until settlement ceases, exchanging the temporary load on each unit for its individual permanent load, and thereafter applying simultaneously to a plurality of the piles a common temporary load at least as great as the common permanent load such plurality of piles is to permanently carry, whereby an enlarged pressure bulb common to said plurality of units is formed beneath said plurality of units, the piles being maintained under load during the exchange and then exchanging such common temporary load simultaneously as to each unit in such plurality ofpiles for the common permanent load to be carried by said plurality of piles.

5. The method of providing a substructure for structures, which consists in setting a footing consisting of a plurality of closely adjacent units, loading each unit with a temporary load and maintaining it under such load until settling of the unit ceases, exchanging the temporary load for a permanent load, and thereafter applying simultaneously to a plurality ofi said units a common temporary load at least as great as the combined common permanent load such plurality of units is to carry, to efiect further settling thereof and until such further settling ceases, and, While said plurality of units is maintained under such common temporary load, exchanging said load simultaneously as to said plurality of units for the common permanent load to be carried by said plurality of units.

In testimony whereof, I have hereunto set my hand.

LAZARUS ITE.

earner 

